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We present the design, fabrication, and characterization of a pixelated, hyperspectral arrayed component for Focal Plane Array (FPA) integration in the Long-Wave IR. This device contains tens of pixels within a single super-pixel which is tiled across the extent of the FPA. Each spectral pixel maps to a single FPA pixel with a spectral FWHM of 200nm. With this arrayed approach, remote sensing data may be accumulated with a non-scanning, "snapshot" imaging system. This technology is flexible with respect to individual pixel center wavelength and to pixel position within the array. Moreover, the entire pixel area has a single wavelength response, not the integrated linear response of a graded cavity thickness design. These requirements bar tilted, linear array technologies where the cavity length monotonically increases across the device.

In this work, we describe the most recent progress towards the device modeling, fabrication, testing and system integration of active resonant subwavelength grating (RSG) devices. Passive RSG devices have been a subject of interest in subwavelength-structured surfaces (SWS) in recent years due to their narrow spectral response and high quality filtering performance. Modulating the bias voltage of interdigitated metal electrodes over an electrooptic thin film material enables the RSG components to act as actively tunable high-speed optical filters. The filter characteristics of the device can be engineered using the geometry of the device grating and underlying materials. Using electron beam lithography and specialized etch techniques, we have fabricated interdigitated metal electrodes on an insulating layer and BaTiO3 thin film on sapphire substrate. With bias voltages of up to 100V, spectral red shifts of several nanometers are measured, as well as significant changes in the reflected and transmitted signal intensities around the 1.55um wavelength. Due to their small size and lack of moving parts, these devices are attractive for high speed spectral sensing applications. We will discuss the most recent device testing results as well as comment on the system integration aspects of this project.

In this paper, we describe progress towards a multi-color spectrometer and radiometer based upon an active resonant subwavelength grating (RSG). This active RSG component acts as a tunable high-speed optical filter that allows device miniaturization and ruggedization not realizable using current sensors with conventional bulk optics. Furthermore, the geometrical characteristics of the device allow for inherently high speed operation. Because of the small critical dimensions of the RSG devices, the fabrication of these sensors can prove challenging. However, we utilize the state-ofthe-art capabilities at Sandia National Laboratories to realize these subwavelength grating devices. This work also leverages previous work on passive RSG devices with greater than 98% efficiency and ~1nm FWHM. Rigorous coupled wave analysis has been utilized to design RSG devices with PLZT, PMN-PT and BaTiO3 electrooptic thin films on sapphire substrates. The simulated interdigitated electrode configuration achieves field strengths around 3×10 7 V/m. This translates to an increase in the refractive index of 0.05 with a 40V bias potential resulting in a 90% contrast of the modulated optical signal. We have fabricated several active RSG devices on selected electro-optic materials and we discuss the latest experimental results on these devices with variable electrostatic bias and a tunable wavelength source around 1.5µm. Finally, we present the proposed data acquisition hardware and system integration plans.

We will discuss a passive thermal emission management surface that can manipulate the direction and wavelength bands of emission. We are designing and fabricating diffractive optics in materials that support surface-polariton plasmons. We use a grating in this material to couple the thermally-generated plasmons to photons. Grating parameters, such as grating depth and duty cycle, are varied to optimize the plasmon/photon coupling efficiency. The grating configuration ensures a phased, radiative response if the plasmon decay length along the surface traverses many grating periods. All of these parameters, material indices and dimensions, determine the specular and angular "shape" of emission.

Massively parallel optical interconnects are appropriate to ease the data bandwidth bottleneck that will occur in future computing applications. Vertical cavity surface emitting lasers (VCSELs) are promising sources for emerging 2D optical systems such as free space and guided wave optical interconnects. We discuss the development of high performance VCSEL arrays, including individually addressable and matrix addressable arrays. We also show the characteristics of GaAs microelectronic driver and photoreceiver chips that have been designed to interface with Si-based CMOS circuitry. Finally, the potential of these source and receiver modules for use in free space or guided wave parallel channel optical interconnect architectures will be described.

Vertical cavity surface emitting lasers (VCSELs) which operate in multiple transverse optical modes have been rapidly adopted into present data communication applications which rely on multi-mode optical fiber. However, operation only in the fundamental mode is required for free space interconnects and numerous other emerging VCSEL applications. Two device design strategies for obtaining single mode lasing in VCSELs based on mode selective loss or mode selective gain are reviewed and compared. Mode discrimination is attained with the use of a thick tapered oxide aperture positioned at a longitudinal field null. Mode selective gain is achieved by defining a gain aperture within the VCSEL active region to preferentially support the fundamental mode. VCSELs which exhibit greater than 3 mW of single mode output power at 850 nm with mode suppression ratio greater than 30 dB are reported.

Optocouplers are used for a variety of applications aboard spacecraft including electrical isolation, switching and power transfer. Commercially available light emitting diode (LED)-based optocouplers have experienced severe degradation of light output due to extensive displacement damage occurring in the semiconductor lattice caused by energetic proton bombardment. A new optocoupler has been designed and fabricated which utilizes vertical cavity surface emitting laser (VCSEL) and resonant cavity photodetector (RCPD) technologies for the optocoupler emitter and detector, respectively. Linear arrays of selectively oxidized GaAs/AlGaAs VCSELS and RCPDS, each designed to operate at a wavelength of 850nm, were fabricated using an airbridge contacting scheme. The airbridged contacts were designed to improve packaging yields and device reliability by eliminating the use of a polyimide planarizing layer which provided poor adhesion to the bond pad metallization. Details of the airbridged optocoupler fabrication process are reported. Discrete VCSEL and RCPD devices were characterized at temperatures between {minus}100 to 100 C. Devices were packaged in a face-to-face configuration to form a single channel optocoupler and its performance was evaluated under conditions of high-energy proton bombardment.

Large area, HgCdTe MW photovoltaic detectors have been developed at Honeywell Electro-Optics Division for the NASA-HALOE instrument. This instrument is scheduled for operation on the Upper Atmospheric Research Satellite (UARS). The photodiodes will be TE cooled and were designed to operate in the 5.1 μm - 5.4 μm band at 185 K to measure Nitric Oxide (NO) concentrations in the atmosphere. To achieve the D* goal of 6 x 109 cm-Hz1/2/W and to meet the spatial responsivity uniformity specification of ± 5% across the 0.6 mm diameter, active area required 15 μm thick devices and a full backside common contact,. Reflections from the backside contact doubled the effective thickness of the detectors. Optical interference from reflections was eliminated with a dual layer front surface A/R coating. Bakeout reliability was optimized by having Au metallization for both n and p interconnects. Detailed performance data and a model for the optical stack are presented.